132 



TICKS. Acarina, 



The cattle tick (Margaropus annulatus australis) occurs 

 throughout the West Indies. It is one of the mites, and not 

 a true insect. The adull (Fig. 143) is reddish-brown in 

 colour: the skin or integument is leathery in texture ; the 

 number of legs is eight. The length of a large female is 

 about |-inch. The male is smaller and Matter than the 

 female, which when fully fed is very much distended. The 

 immature ticks are similar in general appearance to the 

 adult male, being small and flat with comparatively long 

 legs. The newly hatched larvae have only three pairs of 

 legs, the fourth pair being acquired at the first moult. 



The replete egg-laying female, as seen from above 

 appears to be nearly all abdomen, the head and thorax being 

 represented by a very small area at the anterior end of the 

 body. 



The eggs (Fig. 144) are laid on the ground, each female 

 producing great numbers from 1,500 to 3,000. The young, 



six-legged larvae cluster upon grass 

 and low herbage, where they await 

 the passing of cattle or other ani- 

 mals to which they may attach 

 themselves. As soon as these 'grass 

 ticks' or 'seed-ticks' findthem selves 

 on a suitable host, they insert the 

 mouth parts and begin at once to 

 feed. These ticks do not leave the 



r g ' 'f 4 'f , C f tle .. tlck host animal until the life-cycle is 



female tick depositing ^ .. ,. , J 



eggs. Natural size. complete; they moult, become sexu- 



(Fi-om U.S. Dept. Agric.) ally mature, the union of the sexes 



occurs, and then the female, ready 

 to begin egg-laying, drops to the ground. 



The time occupied by the West Indian cattle tick in 

 completing its life-cycle does not seem to have been worked 

 out, but, in the United States, Margaropus annulatus has 

 been found to require about 6 or 7 weeks, divided as 

 follows : 



The first (larval) period occupies 6 or 7 days, the second 

 (nymph) also 6 or 7 days. The adult remains on the host 

 another 5 days, during which time mating occurs, and at 

 the end of this, the impregnated female drops to the ground. 

 Another 3 days ensues before egg-laying begins, and the 

 time required for the eggs to hatch is about 21 days. 



